摘要
致密凝灰质砂岩作为一种特殊的致密砂岩类型,其孔隙结构、孔隙度—渗透率配置关系与普通致密砂岩相比有较大差异,沿用常规传统致密砂岩储层分类方法难以满足该类储层分类评价的需要。以松辽盆地南部德惠断陷营城组致密凝灰质砂岩为研究对象,以核磁共振和压汞实验为主要手段,探究了致密凝灰质砂岩储层孔隙结构特征,分析对比了其与常规致密砂岩孔隙结构的区别。运用相关性分析法,综合考虑储层的渗流能力和有效储集能力,优选出R_(50)(进汞饱和度为50%时所对应的喉道半径)和可动流体饱和度,建立针对致密凝灰质砂岩的储层分类标准。结果表明:该区优质储层主要发育粒间、粒内溶蚀孔等较大尺度有效孔隙,具有明显偏右的T_(2)谱峰值,可动流体饱和度较高;储层主要发育凝灰质溶蚀孔、晶间孔等小尺度孔隙,具有明显偏左的T_(2)谱峰值。以高压压汞和恒速压汞为手段分析孔隙结构特征,识别出大孔—细喉、中孔—细喉、中孔—微喉和小孔—微喉4类典型压汞曲线,对应的凝灰质含量逐渐升高,分析认为凝灰质堵塞关键喉道进而降低渗透率是造成孔渗相关性差的主要原因。结合微观评价参数对致密凝灰质储层和常规致密储层进行对比,发现致密凝灰质储层发育更多小孔,孔渗相关性比常规致密储层更差,核磁共振T2谱与压汞曲线显示出凝灰质储层的有效储集能力和孔隙连通性都不如常规致密储层。运用R50与可动流体饱和度新建储层分类标准,将致密凝灰质砂岩储层划分为Ⅰ、Ⅱ、Ⅲ类储层和干层,分类结果与现场试气结果吻合度较高。
Tight tuffaceous sandstone is a special type of tight sandstone.Its pore structures and porosity permeability relationships are quite different from those of conventional tight sandstone.It is difficult to classify and evaluate the tight tuffaceous sandstone by using conventional reservoir classification methods.This paper studied the tight tuffaceous sandstone of Yingcheng Formation of Dehui fault depression in southern Songliao Basin,where Nuclear Magnetic Resonance(NMR)and high pressure mercury injection are the main means.Pore structure characteristics of tight tuffaceous sandstone are analyzed and the differences with conventival tight sandstone are compared.Correlation analysis was adopted where R_(50)(The throat radius corresponding to the mercury saturation of 50%)and movable fluid saturation are selected as the key parameters to establish a comprehensive new evaluation model for reservoir classification of tight tuffaceous sandstone.Results demonstrate that premium tight tuffaceous sandstone develops intergranular and intragranular dissolution effective pores,has noticeable right-sided T_(2) spectrum distribution and high movable fluid saturation,while inferior tight tuffaceous sandstone mainly has tuffaceous dissolution pores and intercrystalline pores and left-sided T_(2) sepctrum.In addition,the pore structure characteristics were analyzed by means of high pressure mercury injection and constant velocity mercury injection,and four typical mercury injection curves were identified,i.e.,large pore-tiny throat,middle pore-tiny throat,middle pore-micro throat and small pore-micro throat.The corresponding tuffaceous content gradually increases,and it was believed that the main reason for poor correlation between porosity and permeability was that tuff blockes key throats and then decreases permeability.Pore structures between tight tuffaceous sandstone and conventional tight sandstone are compared and analyzed.Tight tuffaceous sandstone developes more tiny pores,has worse porosity-permeability correlations,less effective storage capability and connectivity than conventional tight sandstone.R50 and movable fluid saturation are adopted and tight tuffaceous sandstond reservoirs are divided into typeⅠ,Ⅱ,Ⅲreservoirs and dry reservoir,where the classification results coincide with the testing results.
作者
石晓敏
位云生
朱汉卿
王晨辉
黄苏琦
程敏华
SHI Xiaomin;WEI Yunsheng;ZHU Hanqing;WANG Chenhui;HUANG Suqi;CHENG Minhua(PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2023年第10期1828-1841,共14页
Natural Gas Geoscience
基金
中国石油基础性前瞻性项目“致密气勘探开发技术研究”(编号:2021DJ21)下属课题2“致密气新区开发评价与开发技术研究”(编号:2021DJ2102)资助.
关键词
致密凝灰质砂岩
储层分类
压汞
核磁共振
储集能力
渗流能力
Tight tuffaceous sandstone
Reservoir classification
Mercury injection
Nuclear magnetic resonance
Storage capacity
The seepage ability
